EE 312_Man

EE 312
Fundamentals of Electronics LAB
LAB Manual
By
Turki Almadhi,
Lecturer, EE Dept.
Version
3.1
30/30/2014
1
Course Policy
Instructor
E-mail
Turki Almadhi
[email protected]
Ghazi Isaac
[email protected]
Ahmed Telba
[email protected]
URL
faculty.ksu.edu.sa/almadhi
faculty.ksu.edu.sa/54622/default.aspx
faculty.ksu.edu.sa/atelba/default.aspx
Lab Manual: http://faculty.ksu.edu.sa/almadhi/courses/Documents/ee312/EE312_Man.pdf
Objective: To introduce the student to the basic electronic devices and their applications as well as
building circuit construction skills.
Grading Policy:
Attendance/ Quizzes
15%
Lab Sheet
20%
Reports
10%
Midterm
25%
Final
30%
Quizzes:
Periodic quizzes are to be expected at the first 10 minutes of each lab session.
Reports:
Computer written reports are to be submitted one week after selected experiments (See the course
schedule.) Your report should take the following form:








Cover sheet (Exp. Title; Date ; Section No. ; Name and SID No.)
Objective
List of Equipment
Circuit diagram(s)
Brief procedure
Results and Calculations
Conclusion and Comments
Appendix: Lab Sheet
You will not be allowed to submit a report for an experiment that you haven't attended.
0
Course Schedule
Lab Sheet
Required?
Report
Required?
Lab 1
yes
no
3
Lab 2
yes
yes
4
Lab 3
yes
yes
5
Lab 4
yes
no
6
Revision
7
Midterm Exam
8
Lab 5
yes
yes
9
Break
10
Lab 6
Go to AC 123
11
Lab 7
quiz 2
yes
yes
12
Lab 8
yes
no
13
Lab 9
yes
no
14
Lab 10
yes
yes
15
Revision
16
Final Exam
Week No.
Activity
2
notes
quiz 1
quiz 3
0
LAB1
An Introduction to Semiconductor Diodes
1.1 Objective
To identify the common types of semiconductor diodes, explore their basic principle of operation and learn
the method of their testing.
1.2 Introduction
A p-n junction diode is a two-terminal electronic component with low resistance to current flow in one
direction, and very high resistance in the other. The p-side of the junction is called the anode while the nside is called the cathode (see Fig. 1a). A diode allows an electric current to pass from the anode to the
cathode (called the diode's forward direction), while blocking current in the opposite direction (the reverse
direction). In DC circuits, a forward-biased diode can be approximately modeled by a constant voltage that
depends on its type and characteristics. On the other hand, a reverse-biased diode can be modeled by a
very high resistance or an open circuit.
Figure 1 (a) Diode shape and symbol. (b) Testing a diode using a DMM.
1.3.1 Procedure A: How to Test a Diode
1. Set your Digital Multi-Meter (DMM) dial to diode-test position. Use appropriate mode if applicable.
2. Connect any type of diode between the (V/Ω) terminal and the COM terminal of the DMM (Fig. 1b).
Observe the DMM reading.
3. Determine the anode of each diode based on the approximate expected values given in Table 1.
Table 1
Type of diode
Si
Ge
zener
LED
Test position reading if forward-biased
(Anode connected to (V/Ω) terminal)
0.6 ~ 0.7 V
0.2 ~ 0.4 V
0.6 ~ 0.7 V
1.5 ~ 2 V
4
Test position reading if reverse-biased
(Anode connected to COM terminal)
OL / DMM test voltage
OL / DMM test voltage
OL / DMM test voltage
OL / DMM test voltage
Explanation:
The DMM will display (OL / test voltage) if the diode is reverse-biased. In this case no current flows from
the battery of DMM into the diode and the anode of the diode will be connected to the COM terminal of
the DMM. If, however, it shows a numerical value-the forward voltage drop on the diode, the anode will be
connected to the (V/Ω) terminal).
1.3.2 Procedure B: Diodes in Action
1. Make sure that your DMM is set to measure DC voltage.
2. Connect the circuit shown in Fig. 2 setting Vs initially at 4 V.
3. Start with by connecting a Si diode in the forward direction between nodes A and B. Observe and
record the VAB, and V1-kΩ (to see if there is a current flow.) Reverse the diode direction and repeat the
two measurements. Record your results in Table 2.
Note: The voltage across the 1-k Ω resistor will give you an indication whether a current is actually flowing
in the circuit or not. A higher voltage indicates a higher current (Ohm’s law.)
4. Do the above step for the LED and the zener diode (two cases for the reverse bias as in Table 2.)
5. Connect two Si diodes in series (in forward direction) between nodes A and B. Observe and record the
readings of the DMMs (case 7). Reverse one of them (back-to-back connection) and record your results
(case 8.)
Figure 2 Exploring the behavior of diodes.
Table 2
Diode
Connection
VS (V)
Si
Si
LED
LED
Zener
Zener
Zener
Case 7
Case 8
forward
4
4
4
4
4
2
7
4
4
Reverse
forward
Reverse
forward
Reverse
Reverse
2 forward
back to back
VAB (V)
5
V1-kΩ (V)
Is there current?
(Yes/No)
1.4 Conclusion and Comments
Write down a conclusion for this experiment. Your conclusion should cover the following:
 The general idea of procedure A as well as procedure B.
 The most important things you have learned from these two procedures.
 Any comments you would like to add.
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6
LAB 2
Diode i-v Characteristics
2.1 Objective
To measure the i-v characteristics of two common types of diodes, estimate some parameters from those
measurements and extract a piecewise-linear model for the Si diode.
2.2 Background
The relationship between a diode’s voltage and its current is an exponential one. It can be shown that:
ID = IS [exp(VD /nVT) – 1]
(1)
A diode’s voltage does not change much even with a significant change in its current. In that regard:
VD2 - VD1 = (2.3) n VT log (ID2 / ID1)
(2)
(See textbook)
2.3 Procedure
1. Measure and record the actual value of R.
2. Connect the circuit shown in Fig. 1a. Start with VS = 11 V decreasing VS in steps as given in the Table 1.
For each value of Vs, measure VD and VR and calculate the corresponding value of ID (ID= IR = VR /R).
3. Replace the Si diode with a zener diode and repeat step 2.
Note: for the last six entries in the table you have to reverse the polarity of VS.
Figure 1 (a) Measuring the I-V characteristics. (b) A linear model of a forward –biased diode.
Table 1
R=
VS (V)
11
8
6
3
VR (V)
Si diode
VD (V)
kΩ
ID = VR /R (mA)
7
VR (V)
Zener diode
VD (V)
ID = VR /R (mA)
1.6
1
0.5
0.4
0.2
0
-3
-4
-4.5
-5
-5.5
-10
0
0
0
0
0
0
2.4 Calculations and Questions
1. Plot ID vs. VD for both diodes using MATLAB® (See Appendix A.)
2. Now, we will extract a piecewise-linear model for the Si diode in the forward biased region (Fig. 2)
in the range of 1 mA-10 mA.
i. Find VD@1mA and VD@10mA from your graph (Fig. 3.)
ii. Using rD = (VD@10mA - VD@1mA) / (10 mA – 1 mA), calculate rD. Draw a line between these two
points and extrapolate it on the VD axis to find VDo (see Fig. 3.)
iii. Using the piecewise-linear model you have found above and the value of VS in the first row of
the table, calculate ID and VD and compare that to measured values (in the table.)
3. Calculate n for the Si diode using equation (2) in section 2.2.
Note: (V D1 = VD@1mA , ID1 = 1 mA ) and (VD2 = VD@10mA , ID2 = 10 m)
VT = 26 mV @ room temp.
4. Knowing n and VT, calculate IS from any pair of measurement using equation (1) in section 2.2.
5. Propose a model for the Si diode in reverse bias regime (VD ˂ 0).
Figure 3 Extracting rD and VDo from the i-v Characteristics.
8
LAB 3
Limiter Circuits
3.1 Objective
To explore the basic principles of limiter (clipper) circuits, be able to design them and predict their transfer
characteristics.
3.2 Background
Limiting or clipping is a function performed by a diode network if prevention of the output signal from
exceeding or falling below a predetermined voltage level is desired. A diode is suitable for this role because
its voltage changes a little for a significant change in its current. A single limiter circuit is shown in Fig. 1a,
whereas double limiters are shown in the last three parts of the same figure.
3.3 Procedure
1. Connect the circuit shown in Fig. 1a. Use a sinusoidal input with f = 1 kHz and Vi(p-p) = 5 V.
2. Display ( )(on Channel 1)and ( ) (on Channel 2)of your oscilloscope. Use appropriate vertical and
horizontal sensitivities. Note: Use DC coupling on both channels, and take note of the used sensitivities.
3. Sketch ( )and ( ) on one grid.
Step 4
Transfer Characteristics
circuit (a)
Y2 (V/DIV)=
Y1 (V/DIV)=
Y2 (V/DIV)=
Step 5
Input and output
circuit (b)
Step 5
Transfer Characteristics
circuit (b)
Y1 (V/DIV)=
Y2 (V/DIV)=
Y1 (V/DIV)=
Y2 (V/DIV)=
Step 3
Input and output
circuit (a)
Y1 (V/DIV)=
9
4.
5.
6.
7.
Set your scope on X-Y mode. Sketch the transfer characteristics ( ( ) vs. ( )).
Connect the circuit shown in Fig. 1b. Redo step (3) then (4).
Connect the circuit shown in Fig. 1c. Use a sinusoidal input with Vi(p-p) = 14 V. Redo step (3) then (4).
Connect the circuit shown in Fig. 1d. Redo step (3) then (4).
Step 6
Input and output
circuit (c)
Step 6
Transfer Characteristics
circuit (c)
Y1 (V/DIV)=
Y2 (V/DIV)=
Y1 (V/DIV)=
Y2 (V/DIV)=
Step 7
Input and output
circuit (d)
Step 7
Transfer Characteristics
circuit (d)
Y1 (V/DIV)=
Y2 (V/DIV)=
Y1 (V/DIV)=
Y2 (V/DIV)=
Figure 1 (a) Single limiter (b), (c), and (d) Double limiters
13
3.4 Calculations and Questions
1. Sketch a circuit that will have a transfer characteristic like the one shown in Fig. 2a. Assume that a
Si diode has a forward voltage drop of 0.6 V.
2. For the circuit shown in Fig .2b, sketch the transfer characteristics.
3. From your results in step 6, estimate the zener breakdown voltage, VZ.
Show how you obtained that value.
4. A sinusoidal input of 10-V amplitude is applied to the circuit shown in Fig. 2c. Sketch the output
voltage, using the above value of VZ and assuming a forward voltage drop of 0.7 V.
Figure 2
11
LAB 4
AC to DC Conversion
4.1 Objective
The main aim of this experiment is to introduce the student to the principle of AC to DC conversion which
involves rectification, filtering and voltage regulation.
4.2 Background
Rectifiers use the unidirectional-current property of diodes to convert AC voltage to DC. Capacitors are
used to reduce the ripple of the resulting output. Voltage regulators, as the simple one used in this
experiment, are used to regulate the DC output voltage against load and/or AC input variations.
The full-wave rectified signal average value may be calculated by:
(
(
(
)
)
)
(1)
4.3 Procedure
1. Connect the circuit shown in Fig. 1a. Use a decade box to vary RL; for starters, set RL at 1 kΩ.
Use the (Line) trigger setting of the scope to get steady display. Also, set the scope on (DC) coupling to
display the required signal(s).
2. Display VS(t) on channel (1) and VO (t) on channel (2) of your oscilloscope.
3. Sketch VS (t) and VO (t) on one grid. Take note of the peak value of VS (t).
4. Measure VO(DC) by connecting a multi-meter in parallel with RL. Record your result in the given space.
Set the vertical sensitivity of channel 2 at 1 V/Div, aligning its ground (GND) at the bottom of the screen.
5.
6.
7.
8.
9.
Connect a 10-µF capacitor across the load; sketch VO (t).
Increase RL up to 13 kΩ in 1-kΩ steps, noting its effect on VO (t)’s ripple; sketch VO (t) for RL=13 kΩ.
Add a 470-µF capacitor across the load; sketch VO (t). Note the change on the output’s ripple.
Connect a zener diode across the output; sketch VO (t).
Now, reduce RL down to 1 kΩ in 1-kΩ steps noting its effect on VO (t)’s ripple.
Sketch VO (t) for RL=1 kΩ.
Step 0,4
RL = 1 kΩ
VO(DC)=
Step 5
Y1 (V/DIV)=
Y2 (V/DIV)=
Y2 (V/DIV)=
10
CL = 10 µF
RL = 1 kΩ
Step 6
CL = 10 µF
RL = 13 kΩ
Step 7
Y2 (V/DIV)=
Step 8
CL = (10 +470) µF
RL = 13 kΩ
Y2 (V/DIV)=
CL = (10 +470) µF
RL = 13 kΩ
zener connected
Step 9
Y2 (V/DIV)=
CL = (10 +470) µF
RL = 1 kΩ
zener connected
Y2 (V/DIV)=
4.4 Conclusion and Comments
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Figure 1 A simple DC power supply using a center-tapped transformer.
10
LAB 5
Applications of the Operational Amplifier
5.1 Objective
To get acquainted with the operational amplifier (op amp) through two of its applications: a noninverting
amplifier and a comparator to sense light intensity change.
5.2 Background
The op amp is an integrated circuit (IC) that amplifies the difference between two input voltages and
produces a single output. It is characterized by very large input impedance, very small output impedance
and a very large open-loop gain (A). Stable gains can be obtained using negative feedback. For a
noninverting configuration (Fig. 1(a)), the closed-loop gain (G) can be found by:
(1)
In open-loop configuration, the op amp can be used as a comparator (Fig. 1(b)). For that circuit, and since
the op amp draws negligible current, V+ and V- (with respect to ground) can be found by:
V+ = [(
)
(
)]
(
)
(
V- = [(
) ;
)
(
)]
(
)
(
)
(2.a; 2.b)
On the other hand, a photocell (also called photoresistor or light dependent resistor, LDR) is a resistor whose
resistance decreases with increasing incident light intensity. It is made of a high resistance semiconductor such as
cadmium sulfide (CdS).
5.3.1 Procedure A: Noninverting Amplifier
1. Connect the circuit shown in Fig. 1a. Set your input sinusoidal at 1 V (peak to peak) and a frequency of 1
( ). Measure the peak-to-peak value of the
kHz. Start with R2 of 10 kΩ. Display and sketch ( )
output and determine the closed-loop gain using: G = Vo(p-p)/Vi(p-p). Record that in Table 1.
2. Change R2 to 100 kΩ ; display and sketch
Step 1
Y1 ___
Y1 (V/DIV)=
Y2 (V/DIV)=
( )
( ).
Y2 _ _ _ _
14
Step 3
Y1 ___
Y2 _ _ _ _
Y1 (V/DIV)=
Y2 (V/DIV)=
Table 1
R2 value
13 kΩ
133 kΩ
Vo(peak-peak)
Measued Gain
Theoritical Gain (eqn 1)
xxxxxxxxxxxxxxxxx
Undefined; output clipped
5.3.2 Procedure B: Detecting Light Intensity Change
1. Measure the resitance of a covered and uncovered photocell by a multimeter and record that in Table 2.
2. Connect the circuit shown in Fig. 1b. Measure V+, V-, and Vo (with respect to ground) usign a multimeter.
Which LED glows? Record your findings in Table 2.
3. Cover the photocell (LDR) with the back of your hand and repeat the previous step.
Table 2
Rcell (uncovered):
case
uncovered
covered
Rcell (covered):
V
+
V
-
Vo
which LED glows?
5.4 Calculations and Questions
( ). Sketch a circuit that will
1. In step 1 of procedure A, comment on the phase shift between ( )
o
give the same gain magnitude with a 180 phase shift. What is its common name?
2. In step 2 of procedure A, what has happened to the shape of
or R2 (R2max) which will produce unclipped output.
( )? Why? Calculate the maximum value
3. Calculate V+ and V- using equations (2.a, 2.b). Compare that to the measured values in procedure B.
4. What will happen if you swap external connections of V+ and V-?
Figure 1 Op Amp circuits: (a) noninverting amplifier (b) comparator to sense light intensity change.
15
LAB 6
Computer Simulation of Electronic Circuits
6.1 Clipper Circuit:
1. Double click the OrCAD Capture icon on the desktop.
2. Go to File  New Project. Your project should be named: ckt1_xxxx, where xxxx stands for the last
four digits of your SIDN. Keep the first choice selected. In the second window select: Create a blank
project then click OK.
3. Put together the circuit shown in Figure 1. Use (VAC/SOURCE) for your input V1 with a value of 1Vac
and 0Vdc.
4. From PSpice (top menu), select: New Simulation Profile. Name it for example: dc_sweep. Set
analysis type at: DC Sweep. Sweep V1 from -10 to 10V with appropriate increment.
5. Place a voltage/level marker on the cathode of D1 (the output).
6. Run your circuit to see its transfer characteristics. Change V2 to 7 volts then rerun.
7. Change your input source to (VSIN) with 10V amplitude, 1kHz frequency and V OFFSET = 0.
8. From PSpice (top menu), select: New Simulation Profile. Name it for example: time_domain. Set
analysis type at: Time Domain. Start from 0 up to 3 ms with appropriate maximum step size.
9. Place a voltage/level marker on the cathode of D1 (the output).
10. Run your simulation to display ( ).
R1
+
1k
Vout
D2
D1N4002
V1
VOFF = 0
VAMPL = 10
FREQ = 1ki
D1
D1N4002
V2
5Vdc
V1
5Vdc
-
0
Figure 1
16
6.2 Inverting Amplifier:
1. Start a new project: ckt2_xxxx, where xxxx stands for the last four digits of your SIDN.
2. Put together the circuit shown in Figure 2. Use (VAC/SOURCE) for your input V3 with a value of 1Vac and
0Vdc.
3. Create a new simulation profile of type: AC Sweep. Run your simulation to find the circuit frequency
response (i.e., how the voltage gain changes with frequency).
4. Notice that this simulation profile also calculates the bias point (DC voltages and currents). Use the
appropriate icons from the above menu to display them.
5. Change your input source to (VSIN) with 1-V amplitude, 1-kHz frequency and 0 VOFFSET.
6. Create a new simulation profile of type: Time Domain. Run your simulation to measure the gain. Compare
this value to that in the previous step.
V1
15Vdc
3
R1
V3
1k
U1 7
+
V+
OS2
OUT
2
-
4
uA741
OS1
VV2
15Vdc
1Vac
0Vdc
0
R2
10k
0
Figure 2
17
5
6
1
V
LAB 7
N-MOSFET i-v Characteristics
7.1 Objective
To introduce the student to the MOSFET (Metal Oxide Semiconductor Field Effect Transistor,) examine its
i-v characteristics and measure some of its important parameters. The MOSFET that will be used in this
experiment is the IRF620.
7.2 Background
The MOSFET is a three-terminal device that is used mainly as an electronic switch (in triode and cutoff
modes of operation) or as an amplifier (in saturation mode.) Saturation mode is characterized by a weak
dependence of ID on VDS and a much greater dependence on VGS. The value of VGS at which a conducting
channel between the drain and the source is formed is called the threshold voltage, Vt. To act as a good
amplifier a MOSFET has to have a high transconducatnce, gm; it reflects how much the drain current will
change for a small change in VGS –in saturation.
7.3.1 Procedure A: Threshold Voltage Measurement
1. Connect the circuit shown in Fig. 1.
2. Increase VDD until V1k becomes 0.25V (250 mV).
3. At that point, measure and record the value of VGS using a DC voltmeter.
That value of VGS will approximately be equal to the threshold voltage, Vt (Vt
VGS.)
Threshold voltage (Vt) = …………………
Figure 1 Measuring the threshold voltage, Vt.
7.3.2 Procedure B: Output (Drain) Characteristics Measurement
1. Connect the circuit shown in Fig. 2.
2. Set VGS at (Vt +0.1); Vt being as measured in procedure A. Verify this value using a voltmeter.
3. Vary VDD to obtain VDS values as shown in Table 1. For each value of VDS, measure and record VRD.
The corresponding values of ID can be found from Ohm's law.
4. Set VGS at (Vt +0.2); verify this value using a voltmeter. Redo step 3.
5. Set VGS at (Vt +0.3); verify this value using a voltmeter. Redo step 3.
6. Increase VGS by only 0.01. Measure the resulting change in ID (∆ID.)
18
Figure 2 Measuring the iD-vDS characteristics.
Table 1
VGG = VGS1 = Vt +0.1 V
VGG = VGS2 = Vt +0.2 V
VGG = VGS3 = Vt +0.3 V
VDS
(V)
0
VDS
(V)
0
VDS
(V)
0
VRD
(V)
0
ID
(mA)
0
VRD
(V)
0
ID
(mA)
0
.02
.02
.02
.05
.05
.05
0.1
0.1
0.1
0.2
0.2
0.2
0.5
0.5
0.5
1
1
1
2
2
2
VRD
(V)
0
ID
(mA)
0
∆ID for ∆VGS=0.01:
7.4 Calculations and Questions
1. Use MATLAB® (See Appendix A) to plot ID (mA) vs. VDS (V) for each value of VGS. Label each curve
with the corresponding values of VGS. Also, show VDS(sat) for each curve. What is the shape of the
relationship between ID and VDS(sat)? Label the three regions of operation on your graph (cutoff,
triode, saturation).
2. Calculate k
'
n

w
for this MOSFET using any pair of measurement s (VGS and ID) in saturation.
L
3. From step 6 of procedure B, calculate gm which, in saturation, is defined as: g m 
Verify that value using: g m 
I D
.
VGS
2I D
. Compare the two values of gm and comment.
VGS  Vt
19
LAB 8
VTC and Large Signal Operation of the CS Circuit
8.1 Objective
To study the voltage transfer characteristic (VTC) of the common-source circuit and learn its implications
on using it as a common-source amplifier or as a passive-load inverter.
8.2 Background
A great deal of information can be learned for a specific circuit by studying its VTC. For example, the region
characterized by a high gain can be utilized for voltage amplification. In contrast, regions characterized by
maximum or minimum output voltage levels may be taken advantage of in switching. If a square wave is
applied to the input of the common-source circuit, it acts as a logic inverter. An inverter loaded with
capacitance will respond sluggishly due to RC delay caused by the requirement to charge and discharge the
capacitive load.
8.3.1 Procedure A: VTC for the Common Source Circuit
4. Connect the circuit shown in Fig. 1a.
5. Set your scope at X-Y mode. Connect your input to channel 1 and your output to channel 2. Set
your sensitivities @ 1 V/DIV for both channels.
6. Use a decade box to set RD at 10 kΩ then at 1 kΩ. Sketch the transfer characteristics for each case
on the same graph.
Figure 1 (a) The common-source circuit; (b) Its VTC.
8.3.2 Procedure B: Large signal Operation: the passive-load Inverter
1. Apply a square wave (From the TTL output of your signal generator) to the circuit in Fig.1a. Leave
the value of RD as it is. Sketch the input and the output as they appear on the scope.
2. Connect a 10-nF loading capacitor (CL) across the output. Sketch the output waveform.
3. Replace the 10-nF capacitor with a 100-nF one. Sketch the output waveform.
03
VTC for the CS circuit
Procedure B
Step 1
Y1 ___
Y2 _ _ _ _
Y1 (V/DIV)=
Y2 (V/DIV)=
Procedure B
Step 2, 3
CL=10 nF ___
CL=100 nF _ _ _ _
Y1 (V/DIV)=
Y2 (V/DIV)=
8.4 Calculations and Questions
1. In procedure A:
a. For a square wave input (0 to 5 V), between which two modes will the MOSFET operate?
b. For RD = 1 kΩ, what is the value of DC offset required to operate this circuit as an amplifier?
c. Which value of RD gives us a higher gain AV? How is the gain related to the slope?
2. In procedure B:
a. The rise time of a waveform, tr, is the time it takes to increase from 10% to 90% of its final
value. How does the capacitance affect tr of Vout? Also, discuss how RD affects tr.
01
LAB 9
VTC of the Common-Emitter Circuit
9.1 Objective
To introduce the student to the npn Bipolar Junction Transistor (BJT) by studying the voltage transfer
characteristic (VTC) of a simple common-emitter (grounded emitter) circuit.
9.2 Background
The BJT is a three-terminal device that is used mainly as an electronic switch (by operating it in saturation
and cutoff modes) or as an amplifier (in active mode.) In general, for an npn BJT:
VBC = VBE - VCE
(1) and
IE = IB + IC
(2)
If VBE < 0.5 V  IB = IC = IE = 0, and the BJT is said to be cutoff.
If VBE ≈ (3.5 ~ 3.7) V and VBC ≤ 3.4 V, the BJT will be operating in the active mode. In this case,:
β = IC / IB
(3) and
α = IC / IE
(4)
If VBE ≈ (3.5 ~ 3.7) V and VBC > 0.4 V, the BJT will be saturated and VCE(sat) ≈ (3.1 ~ 3.0) V.
For the CE circuit shown in Fig. 1:
IB = (Vin – VBE)/RB
(5) and
IC = (VCC – Vout) / RC
(6)
9.3 Procedure
1. Connect the circuit shown in Fig. 1. Fix VCC at 5 V and vary Vin in steps as shown in Table 1. For each
value of Vin measure VBE and VCE (Vout.)
2. Do the required calculations in Table 1 using the relevant equations given in section (9.2.)
Table 1
Measurements
Vin (V)
VBE (V)
VCE = Vout (V)
VBC (V)
0
0.3
0.5
0.8
1
1.5
0
5
-5
2
2.6
2.8
3
3.2
3.5
3.7
4
4.5
5
00
Calculations
Mode of
IB
operation?
(mA)
Cutoff
IC
(mA)
9.4 Calculations and Questions
( )
( ) ) on the above graph. Use only the
1. Plot the DC transfer characteristics (
highlighted entries in the table.
2. Label the three modes of operation on graph.
3. Which region of the above characteristics can be used for voltage amplification? Why?
4. Looking at your results in Table 1, comment on:
a. How the collector current IC changes with IB in the saturation mode of operation compared
to the active mode.
b. The bias condition of the base-collector junction in the active mode of operation.
Fig. 1 The Common Emitter Circuit.
00
LAB 10
Common Emitter Amplifier
10.1 Objective
To explore an important application of the BJT, namely using it to amplify (increase the amplitude of) a
small signal. Specifically, a common (grounded) emitter amplifier will be examined from the DC and small
signal perspective.
10.2 Background
The Common Emitter (CE) amplifier is the mostly used of all BJT amplifier configurations. Figure 1b shows
how this amplifier is connected. An emitter degeneration resistance, RE, is used to stabilize the dc bias
point (or quiescent point, Q) against variations in β. Moreover, including RE increases the amplifier’s input
impedance, and increases its linear range. However, it turns out that RE has a negative impact on the
voltage gain. This effect can be remedied by using a bypass capacitor, CE, to bypass RE at signal frequencies.
Coupling capacitors, CC1 and CC2 are used to act as short circuits at signal frequencies of interests while
blocking dc. Last but not least, the CE amplifier is characterized by a 180 phase shift; it’s an indication of
the inverse relationship between its input and output as you may recall from lab 9.
10.3.1 Procedure A: DC Measurements
1.
2.
3.
4.
5.
6.
Measure each resistor by multi-meter and record its value in the table given below.
Connect the circuit shown in Fig. 1a.
Measure and record the values of VBE, VBC, VRB1, VRB2, VRC and VRE.
Indicate the mode of operation (cutoff, saturation or active) based on V BE and VBC.
Calculate IC and IB as indicated in the table.
Calculate β = IC/ IB and α = β/( β +1); insert your results in the provided space below.
RB1 =
RB2 =
RC =
RE =
VBE =
VBC =
VRB1 =
VRB2 =
VRC =
VRE =
(is VBC < 0.4?)
……………….…………… mode
I1 = VRB1/ RB1= I2 = VRB2/ RB2= IC = VRC/ RC=
IE = VRE/ RE=
IB =I1 - I2=
β = IC/ IB =
α = β/( β +1)=
04
10.3.2 Procedure B: Small Signal Measurements
1.
2.
3.
4.
5.
6.
Connect the circuit shown in Fig 1.(b).
With CE disconnected, apply a sinusoidal input signal with a peak-peak value of 20 mV and f = 1 kHz.
Display and sketch Vi (t) and VO (t). What is the phase shift between these two signals?
Measure Vo(p-p) and calculate the voltage gain: AV = Vo(p-p)/ Vi(p-p).
Re-measure AV with CE connected (no need to sketch VO (t) in this case.)
Increase Vin(p-p) to 500 mV; sketch VO (t).
Step 3, 4 and 5
Legend Y1 ____ Y2 _ _ _
Step 6
Legend Y1 ____ Y2 _ _ _
Y1 (V/DIV)=
Av (step 3)=
Phase shift =
Av (step 5)=
Y1 (V/DIV)=
Comment:
Y2 (V/DIV)=
Y2 (V/DIV)=
10.4 Calculations and Questions
5. Do a hand calculation for the circuit shown in Fig. 1a to obtain IB and IC and VBC. Use the measured
values of all resistors, VBE, and β. Compare the results of your calculations with your measurements.
6. What is the role of RE and how does it affect the voltage gain, AV? How can we counteract this effect
at signal frequencies?
7. What are the roles of CC1, CC2 and CE?
8. In step 6 of procedure B, what has happened to the output? Why? Label the maximum and
minimum output levels with the appropriate modes of operation.
05
Appendix A
MATLAB® Code (LAB 2)
% plotting ID-VD characteristics for Si diode and Zener diode
clf
% store voltage readings for Si diode below
VDSi = [
];
% store current readings for Si diode below
IDSi = [
];
% store voltage readings for zener diode below
VDZn = [
];
% store current readings for zener diode below
IDZn = [
];
figure(1)
plot (VDSi,IDSi,‘-dk’,VDZn,IDZn,‘-*k’)
grid on
legend (‘Si diode’,‘Zener diode’)
title (‘The ID-VD characteristics for Si diode and Zener
diode’)
xlabel (‘VD (V)’)
ylabel (‘ID (mA)’)
06
Appendix A
MATLAB® Code (LAB 7)
% plotting ID-VDS characteristics for different values of VGS for NMOS
clf
VDS = [0 0.02 0.05 0.1 0.2 0.5 1 2];
% store current readings for VGS1 below
ID1 = [
];
% store current readings for VGS2 below
ID2 = [
];
% store current readings for VGS3 below
ID3 = [
];
figure(1)
plot (VDS,ID1,‘-ob’,VDS,ID2,‘-dk’,VDS,ID3,‘-*r’)
grid on
legend (‘VGS1’,‘VGS2’,‘VGS3’)
title (‘The ID-VDS characteristics for NMOS’)
xlabel (‘VDS (V)’)
ylabel (‘ID (mA)’)
07
Fundamentals of Electronics Lab Equipment List
Lab
Lab 1
Lab 2
Lab 3
Lab 4
Lab 5
Lab 6
Equipment
Power Supply
DMM
Si diode
LED
Zener diode
Resistor
Rastered socket panel
Bridging plugs
wires
Power Supply
DMM
Si diode
Zener diode
Resistor
Rastered socket panel
Bridging plugs
wires
Signal generator
Oscilloscope
DMM
Si diode
Zener diodes
Resistor
Rastered socket panel
Bridging plugs
wires
Center-tapped xformer
Oscilloscope
DMM
Details
Si diode
Capacitor
Zener diode
Resistance decade box
Resistor
Rastered socket panel
Bridging plugs
wires
Dual power Supply
Oscilloscope
DMM
741 op amp
LED
LDR
Resistors
2
10 µF, 470 µF
1 (4.3 V)
Lab
Lab 7
2
1
1 (4.3 V)
1 kΩ
Lab 8
1
1 (4.3 V)
1 kΩ
Lab 9
2
2 (4.3 V)
1 kΩ
Lab 10
Equipment
Power Supply
DMM
NMOSFET
Resistor
Rastered socket panel
Bridging plugs
wires
Power Supply
Signal generator
Oscilloscope
NMOSFET
Resistor
Capacitors
Rastered socket panel
Bridging plugs
wires
Power Supply
Power Supply
DMM
BJT
Resistor s
Rastered socket panel
Bridging plugs
wires
Signal generator
Oscilloscope
DMM
BJT
Resistors
Capacitors
Rastered socket panel
Bridging plugs
wires
133 Ω
1
2
1
1 kΩ, 13 kΩ, 133
kΩ, 07 kΩ, 09 kΩ
Rastered socket panel
Bridging plugs
wires
OrCAD PCB Designer Lite
08
Details
2
1
1 kΩ
1
1 kΩ, 13 kΩ
10 nF, 100 nF
1
1 kΩ, 47 kΩ
2
473 Ω, 4.7 kΩ,
47 kΩ, 5.6 kΩ
2.2 µF (2), 470 µF
09
03

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